'With the help of ... others,' said Gandalf. ... 'But here beside the mound I will say this for your comfort: many fell in the battles of the Fords, but fewer than rumour made them. More were scattered than were slain; I gathered together all that I could find. Some ... I set to make this burial.' ...

With that the company said farewell to the island and the mound, and passed over the river, and climbed the further bank. Then they rode on, glad to have left the mournful Fords.

The Two Towers, LoTR Book 3, Ch 8, The Road to Isengard

Over the plains Shadowfax was flying, needing no urging and no guidance. ... they had reached the Fords of Isen and crossed them. The Mound of the Riders and its cold spears lay grey behind them.

They stooped then to lift the body, and found that Théodred still breathed; but he lived only long enough to speak his last words: Let me lie here -- to keep the Fords till Éomer comes!

Unfinished Tales, Part 3, Ch 5, The Battles of the Fords of Isen

It is told that [Grimbold] set up on stakes all about the eyot the heads of the axemen that had been slain there, but above the hasty mound of Théodred in the middle was set his banner. "That will be defence enough," he said. [Author's note.]

Unfinished Tales, Part 3, Ch 5, The Battles of the Fords of Isen: Notes, Note 8